Rain sensors are used in vehicles in order to recognize vehicle window panes contaminated by raindrops.
U.S. Published Application No. 2004/0201483 A1 describes an automatic control system of a vehicle. It may be used to activate a cleaning system of a window pane of the vehicle.
To detect an aging condition of a window wiper, a colored dot is printed on the wiper blade. The color changes with the aging condition. This does not, however, provide a useful measure of the particularly relevant real degree of wear of the edge of the wiper.
To produce an optical image of a window pane, an assembly such as the front camera assembly described in German Application No. DE 10 2009 000 004 A1 may be used. Such a camera may be employed to recognize a condition of a window pane, especially with regard to whether it is wetted by rain or contaminated, as described in German Patent Application No. DE 10 2009 000 003 A1.
A system for detecting the condition, or rather the degree of wear, of wiper blades of a window wiper on the basis of detected smears in a picture taken by a camera is described in German Patent Application No. DE 102 54 684 A1. However, German Patent Application No. DE 102 54 684 does not provide a technical teaching as to how the smears are detected in the image.